Investigators were called in to examine an $11.5 million city technology contract yesterday after Comptroller John Liu uncovered what he described as questionable billings that could lead to “potential fraud.”

The comptroller lashed out at managers at the Department of Consumer Affairs, charging they were so obstructive that he aborted the audit in midstream and sent his findings to the Department of Investigation.

Liu’s office had been examining a contract signed in 2007 with Gartner Inc. to oversee an online payment system being built for businesses that are licensed by the DCA and other city agencies. The original deal was for $2.7 million. It has since grown to $11.5 million, with $10.4 million paid.

Among the findings of the aborted audit:

* Consultants who were paid between $210 and $298 an hour submitted some time sheets that appear to have been “created” just for the auditors.

* One time sheet, supposedly from January 2011, listed a Gartner project manager who didn’t start working on the project until February 2012.

* The DCA paid Gartner $113,000 for specialized training of its chief information officer, Christopher Montgomery, that had nothing to do with the contract. Montgomery left in April to become chief technology officer at NJ Transit. He didn’t return calls.

* The DCA failed to claim $65,000 of a $250,000 discount offered by Gartner.

In a letter to Consumer Affairs Commissioner Jonathan Mintz, Liu’s audit chief, Tina Kim, said the level of obstruction by Mintz’s agency made the audit impossible.

Andrew Spender, a spokesman for Gartner, issued a statement saying it had “fully cooperated” with the comptroller.

DCA spokeswoman Abigail Lootens called Liu’s report “irresponsible” and said the DCA “made each requested witness and every one of thousands of documents fully available.”

Lootens insisted there was no hanky-panky with the time sheets.

“They weren’t created,” she said. “A new copy was printed out to fulfill the auditor’s request.” Officials also said that the project’s initial $2.7 million cost was only for a first phase.